Subject: [PATCH v7 38/59] perf failed-syscalls-by-pid: Port failed-syscalls-by-pid to use python module

From: Ian Rogers <[email-masked]>
Date: Sat, 25 Apr 2026 15:49:30 -0700

Ported from tools/perf/scripts/python/failed-syscalls-by-pid.py to use
the perf Python module API.

Key changes:
- Used perf.syscall_name() to resolve syscall names instead of legacy
  Util library.
- Used standard collections.defaultdict for nested statistics
  aggregation.
- Used errno.errorcode for resolving error strings.
- Supported optional filtering by COMM or PID via command line
  arguments.

Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <[email-masked]>
---
v2: Fixed Syscall Name Fallback: Handled the case where
    perf.syscall_name() returns None , falling back to the string
    representation of the syscall ID to avoid TypeError during string
    formatting.

v7:
- Removed dead code (unused self.unhandled dictionary).
---
 tools/perf/python/failed-syscalls-by-pid.py | 116 ++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100755 tools/perf/python/failed-syscalls-by-pid.py

diff --git a/tools/perf/python/failed-syscalls-by-pid.py b/tools/perf/python/failed-syscalls-by-pid.py
new file mode 100755
index 000000000000..eecd553cbf8f
--- /dev/null
+++ b/tools/perf/python/failed-syscalls-by-pid.py
@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""
+Displays system-wide failed system call totals, broken down by pid.
+If a [comm] or [pid] arg is specified, only syscalls called by it are displayed.
+
+Ported from tools/perf/scripts/python/failed-syscalls-by-pid.py
+"""
+
+import argparse
+from collections import defaultdict
+import errno
+from typing import Optional
+import perf
+
+
+def strerror(nr: int) -> str:
+    """Return error string for a given errno."""
+    try:
+        return errno.errorcode[abs(nr)]
+    except KeyError:
+        return f"Unknown {nr} errno"
+
+
+class SyscallAnalyzer:
+    """Analyzes failed syscalls and aggregates counts."""
+
+    def __init__(self, for_comm: Optional[str] = None, for_pid: Optional[int] = None):
+        self.for_comm = for_comm
+        self.for_pid = for_pid
+        self.session: Optional[perf.session] = None
+        self.syscalls: dict[tuple[str, int, int, int], int] = defaultdict(int)
+
+    def process_event(self, sample: perf.sample_event) -> None:
+        """Process a single sample event."""
+        event_name = str(sample.evsel)
+        if "sys_exit" not in event_name:
+            return
+
+        pid = sample.sample_pid
+        if hasattr(self, 'session') and self.session:
+            comm = self.session.find_thread(pid).comm()
+        else:
+            comm = "Unknown"
+
+        if self.for_comm and comm != self.for_comm:
+            return
+        if self.for_pid and pid != self.for_pid:
+            return
+
+        ret = getattr(sample, "ret", 0)
+        if ret < 0:
+            syscall_id = getattr(sample, "id", -1)
+            if syscall_id == -1:
+                syscall_id = getattr(sample, "sys_id", -1)
+
+            if syscall_id != -1:
+                self.syscalls[(comm, pid, syscall_id, ret)] += 1
+
+    def print_summary(self) -> None:
+        """Print aggregated statistics."""
+        if self.for_comm is not None:
+            print(f"\nsyscall errors for {self.for_comm}:\n")
+        elif self.for_pid is not None:
+            print(f"\nsyscall errors for PID {self.for_pid}:\n")
+        else:
+            print("\nsyscall errors:\n")
+
+        print(f"{'comm [pid]':<30}  {'count':>10}")
+        print(f"{'-' * 30:<30}  {'-' * 10:>10}")
+
+        sorted_keys = sorted(self.syscalls.keys(), key=lambda k: (k[0], k[1], k[2]))
+        current_comm_pid = None
+        for comm, pid, syscall_id, ret in sorted_keys:
+            if current_comm_pid != (comm, pid):
+                print(f"\n{comm} [{pid}]")
+                current_comm_pid = (comm, pid)
+            try:
+                name = perf.syscall_name(syscall_id) or str(syscall_id)
+            except AttributeError:
+                name = str(syscall_id)
+            print(f"  syscall: {name:<16}")
+            err_str = strerror(ret)
+            count = self.syscalls[(comm, pid, syscall_id, ret)]
+            print(f"    err = {err_str:<20}  {count:10d}")
+
+
+if __name__ == "__main__":
+    ap = argparse.ArgumentParser(
+        description="Displays system-wide failed system call totals, broken down by pid.")
+    ap.add_argument("-i", "--input", default="perf.data",
+                    help="Input file name")
+    ap.add_argument("filter", nargs="?", help="COMM or PID to filter by")
+    args = ap.parse_args()
+
+    F_COMM = None
+    F_PID = None
+
+    if args.filter:
+        try:
+            F_PID = int(args.filter)
+        except ValueError:
+            F_COMM = args.filter
+
+    analyzer = SyscallAnalyzer(F_COMM, F_PID)
+
+    try:
+        print("Press control+C to stop and show the summary")
+        session = perf.session(perf.data(args.input), sample=analyzer.process_event)
+        analyzer.session = session
+        session.process_events()
+        analyzer.print_summary()
+    except KeyboardInterrupt:
+        analyzer.print_summary()
+    except Exception as e:
+        print(f"Error processing events: {e}")
-- 
2.54.0.545.g6539524ca2-goog